1. Field of the Invention
The present invention relates to a thin film transistor substrate and a manufacturing method thereof, and more particularly, to a thin film transistor substrate and a manufacturing method thereof decreasing a lifting of an organic layer generated around pads.
2. Description of the Related Art
Generally, a conventional liquid crystal display (LCD) often comprises a liquid crystal panel, a backlight unit, a driving part and chassis. Further, the liquid crystal panel comprises a thin film transistor (TFT) substrate having thin film transistors, a color filter substrate and a liquid crystal layer sandwiched between the TFT substrate and the color filter substrate.
A signal line, such as a gate line or a data line etc., is formed on the TFT substrate and a pixel electrode is provided over the signal line. The signal line is connected to a pad provided in non-display area in order to be connected with an outside circuit. A passivation layer is formed between the signal line and the pixel electrode for insulating. The signal line is extended from the pad and is connected to a shorting bar for an array test.
The passivation layer is commonly made of a silicon nitride (SiNx) and can be formed on the signal line through PECVD (plasma enhanced chemical vapor deposition). If the signal line is close to the pixel electrode, cross talk can occur due to the SiNx that is provided as a dielectric layer between the signal line and the pixel electrode, thereby generating a capacitance.
Capacitance is defined as C=∈ A/d. Herein ∈ is a specific dielectric of a dielectric layer, A is an overlap area between the signal line and the pixel electrode and d is a distance between the signal line and the pixel electrode. Capacitance should be decreased by increasing a thickness of the SiNx (the distance between the signal line and the pixel electrode) in order to prevent cross talk from the dielectric layer. However, it is often difficult to form a required thickness of the SiNx through PECVD because it takes so much time. Thus, if only the SiNx is used as the passivation layer, a space between the signal line and the pixel electrode should keep a certain distance in order to decrease the cross talk. However, this lowers the aperture ratio, i.e., the amount of the overall display area that can transmit light.
To solve this problem, an organic layer has been introduced. Because the organic layer is formed through a spin coating or a slit coating on the signal line, not through PECVD, the thickness may be increased. Thus, the pixel electrode may be formed close to the signal line or overlapped thereof, so that the aperture ratio may be increased.
Generally, such an organic layer is formed relatively thin in the non-display area to ensure good electrical contact between the pad and the outside circuit, and between the shorting bar and the signal line. While forming the organic layer thinly in the non-display area, the organic layer near the signal line or the pad is lifted and the signal line is exposed to an etchant for patterning a transparent conductive layer.